ok a friend of mine is doing a full rebuild/turbo for a customer. its finaly all done its in a 99 civic ex and the head was suposed to be a y8 but after they received it and installed it they then discoverd it was a z6 head. we changed the distributor houseings and got the car to run.

problem is the idle jumps from 1k-3k and their is a bad vacume leak where the y8 manifold meets the z6 head. he is using the y8 intake gasket because he thought it was the y8 head. also the head has minor port/polish job for turbo.

any sujestions would be helpful. should we try the z6 gasket? will that fix the leak? what could cause the y8 manifold to leak when bolted on the z6 head?

thanks

 

are you sure the vacuum leak isn't somewhere else. Maybe you forgot to plug something up that needed to be?

 

the air injection holes need to be filled in on the Y8 mani..pull it off and you will see what I am talking about...right above the end of the runners there is a pea hole sized spot that needs to be filled in with something like JBweld or something..i too had this probelm and this is how it was fixed...

 

No harm in trying the z6 gasket. Are you sure the problem isn't with the vacuum hoses to the intake mani? I thought the parts were interchangeable but not sure about that.

 

do u have a pic he said it was leaking from the top of the manifold so this sounds like its the problem

 

search and you will find pics..This is for sure the problem....

 

http://www.we-todd-did-racing....DE%3D

This is a fairly large picture....but shows a manifold with plugged up air-injection holes. I did it a while back, and put a black dot above one port to show where they normally are. You must plug these up if you don't use a 99-00 EX cylinder head.